/**
 * Copyright 2003-2010 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
 * www.source-code.biz, www.inventec.ch/chdh
 *
 * This module is multi-licensed and may be used under the terms
 * of any of the following licenses:
 *
 *  EPL, Eclipse Public License, http://www.eclipse.org/legal
 *  LGPL, GNU Lesser General Public License, http://www.gnu.org/licenses/lgpl.html
 *  AL, Apache License, http://www.apache.org/licenses
 *  BSD, BSD License, http://www.opensource.org/licenses/bsd-license.php
 *
 * Please contact the author if you need another license.
 * This module is provided "as is", without warranties of any kind.
 */

package net.wangliping.android.tools.microblog;

/**
 * A Base64 encoder/decoder.
 * 
 * <p>
 * This class is used to encode and decode data in Base64 format as described in
 * RFC 1521.
 * 
 * <p>
 * Project home page: <a
 * href="http://www.source-code.biz/base64coder/java/">www.
 * source-code.biz/base64coder/java</a><br>
 * Author: Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland<br>
 * Multi-licensed: EPL / LGPL / AL / BSD.
 */

public class Base64Coder {
	// The line separator string of the operating system.
	private static final String systemLineSeparator = System.getProperty("line.separator");

	// Mapping table from 6-bit nibbles to Base64 characters.
	private static char[]    map1 = new char[64];
	   static {
	      int i=0;
	      for (char c='A'; c<='Z'; c++) map1[i++] = c;
	      for (char c='a'; c<='z'; c++) map1[i++] = c;
	      for (char c='0'; c<='9'; c++) map1[i++] = c;
	      map1[i++] = '+'; map1[i++] = '/'; }

	// Mapping table from Base64 characters to 6-bit nibbles.
	private static byte[]    map2 = new byte[128];
	   static {
	      for (int i=0; i<map2.length; i++) map2[i] = -1;
	      for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; }

	/**
	 * Encodes a string into Base64 format. No blanks or line breaks are
	 * inserted.
	 * 
	 * @param s A String to be encoded.
	 * @return A String containing the Base64 encoded data.
	 */
	public static String encodeString (String s) {
	   return new String(encode(s.getBytes())); }

	/**
	 * Encodes a byte array into Base 64 format and breaks the output into lines
	 * of 76 characters. This method is compatible with
	 * <code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.
	 * 
	 * @param in An array containing the data bytes to be encoded.
	 * @return A String containing the Base64 encoded data, broken into lines.
	 */
	public static String encodeLines (byte[] in) {
	   return encodeLines(in, 0, in.length, 76, systemLineSeparator); }

	/**
	* Encodes a byte array into Base 64 format and breaks the output into lines.
	* @param in            An array containing the data bytes to be encoded.
	* @param iOff          Offset of the first byte in <code>in</code> to be processed.
	* @param iLen          Number of bytes to be processed in <code>in</code>, starting at <code>iOff</code>.
	* @param lineLen       Line length for the output data. Should be a multiple of 4.
	* @param lineSeparator The line separator to be used to separate the output lines.
	* @return              A String containing the Base64 encoded data, broken into lines.
	*/
	public static String encodeLines(byte[] in, int iOff, int iLen,
			int lineLen, String lineSeparator) {
		int blockLen = (lineLen * 3) / 4;
		if (blockLen <= 0)
			throw new IllegalArgumentException();
		int lines = (iLen + blockLen - 1) / blockLen;
		int bufLen = ((iLen + 2) / 3) * 4 + lines * lineSeparator.length();
		StringBuilder buf = new StringBuilder(bufLen);
		int ip = 0;
		while (ip < iLen) {
			int l = Math.min(iLen - ip, blockLen);
			buf.append(encode(in, iOff + ip, l));
			buf.append(lineSeparator);
			ip += l;
		}
		return buf.toString();
	}

	/**
	* Encodes a byte array into Base64 format.
	* No blanks or line breaks are inserted in the output.
	* @param in  An array containing the data bytes to be encoded.
	* @return    A character array containing the Base64 encoded data.
	*/
	public static char[] encode (byte[] in) {
	   return encode(in, 0, in.length); }

	/**
	* Encodes a byte array into Base64 format.
	* No blanks or line breaks are inserted in the output.
	* @param in    An array containing the data bytes to be encoded.
	* @param iLen  Number of bytes to process in <code>in</code>.
	* @return      A character array containing the Base64 encoded data.
	*/
	public static char[] encode (byte[] in, int iLen) {
	   return encode(in, 0, iLen); }

	/**
	* Encodes a byte array into Base64 format.
	* No blanks or line breaks are inserted in the output.
	* @param in    An array containing the data bytes to be encoded.
	* @param iOff  Offset of the first byte in <code>in</code> to be processed.
	* @param iLen  Number of bytes to process in <code>in</code>, starting at <code>iOff</code>.
	* @return      A character array containing the Base64 encoded data.
	*/
	public static char[] encode (byte[] in, int iOff, int iLen) {
	   int oDataLen = (iLen*4+2)/3;       // output length without padding
	   int oLen = ((iLen+2)/3)*4;         // output length including padding
	   char[] out = new char[oLen];
	   int ip = iOff;
	   int iEnd = iOff + iLen;
	   int op = 0;
	   while (ip < iEnd) {
	      int i0 = in[ip++] & 0xff;
	      int i1 = ip < iEnd ? in[ip++] & 0xff : 0;
	      int i2 = ip < iEnd ? in[ip++] & 0xff : 0;
	      int o0 = i0 >>> 2;
	      int o1 = ((i0 &   3) << 4) | (i1 >>> 4);
	      int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
	      int o3 = i2 & 0x3F;
	      out[op++] = map1[o0];
	      out[op++] = map1[o1];
	      out[op] = op < oDataLen ? map1[o2] : '='; op++;
	      out[op] = op < oDataLen ? map1[o3] : '='; op++; }
	   return out; }

	/**
	* Decodes a string from Base64 format.
	* No blanks or line breaks are allowed within the Base64 encoded input data.
	* @param s  A Base64 String to be decoded.
	* @return   A String containing the decoded data.
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	*/
	public static String decodeString (String s) {
	   return new String(decode(s)); }

	/**
	* Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.
	* CR, LF, Tab and Space characters are ignored in the input data.
	* This method is compatible with <code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.
	* @param s  A Base64 String to be decoded.
	* @return   An array containing the decoded data bytes.
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	*/
	public static byte[] decodeLines (String s) {
	   char[] buf = new char[s.length()];
	   int p = 0;
	   for (int ip = 0; ip < s.length(); ip++) {
	      char c = s.charAt(ip);
	      if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
	         buf[p++] = c; }
	   return decode(buf, 0, p); }

	/**
	* Decodes a byte array from Base64 format.
	* No blanks or line breaks are allowed within the Base64 encoded input data.
	* @param s  A Base64 String to be decoded.
	* @return   An array containing the decoded data bytes.
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.
	*/
	public static byte[] decode (String s) {
	   return decode(s.toCharArray()); }

	/**
	* Decodes a byte array from Base64 format.
	* No blanks or line breaks are allowed within the Base64 encoded input data.
	* @param in  A character array containing the Base64 encoded data.
	* @return    An array containing the decoded data bytes.
	* @throws    IllegalArgumentException If the input is not valid Base64 encoded data.
	*/
	public static byte[] decode (char[] in) {
	   return decode(in, 0, in.length); }

	/**
	* Decodes a byte array from Base64 format.
	* No blanks or line breaks are allowed within the Base64 encoded input data.
	* @param in    A character array containing the Base64 encoded data.
	* @param iOff  Offset of the first character in <code>in</code> to be processed.
	* @param iLen  Number of characters to process in <code>in</code>, starting at <code>iOff</code>.
	* @return      An array containing the decoded data bytes.
	* @throws      IllegalArgumentException If the input is not valid Base64 encoded data.
	*/
	public static byte[] decode (char[] in, int iOff, int iLen) {
	   if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");
	   while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--;
	   int oLen = (iLen*3) / 4;
	   byte[] out = new byte[oLen];
	   int ip = iOff;
	   int iEnd = iOff + iLen;
	   int op = 0;
	   while (ip < iEnd) {
	      int i0 = in[ip++];
	      int i1 = in[ip++];
	      int i2 = ip < iEnd ? in[ip++] : 'A';
	      int i3 = ip < iEnd ? in[ip++] : 'A';
	      if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
	         throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
	      int b0 = map2[i0];
	      int b1 = map2[i1];
	      int b2 = map2[i2];
	      int b3 = map2[i3];
	      if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
	         throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
	      int o0 = ( b0       <<2) | (b1>>>4);
	      int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
	      int o2 = ((b2 &   3)<<6) |  b3;
	      out[op++] = (byte)o0;
	      if (op<oLen) out[op++] = (byte)o1;
	      if (op<oLen) out[op++] = (byte)o2; }
	   return out; }

	// Dummy constructor.
	private Base64Coder() {}

}
